First of all: you should not try to make vape liquid at all. This stuff gets inhaled and partially absorbed by your lungs, so you should treat it with the same consideration as a medication. I've heard of a case where someone put some regular garden herbs (unfortunately I forgot which herbs, but they were considered harmless cooking ingredients) into a cigarette and it landed them in hospital for 2 days. Don't put any chemicals into your body unless you understand what they do or some professional who knows about this stuff tells you that it's safe.
As a rule of thumb water extracts the taste of an ingredient and oil extracts the smell of it. So if you want to extract the scent of rosemary for an aroma lamp, the usual process is to infuse a neutral carrier oil with the ingredient you want.
Cut the ingredient very fine and put them into an airtight container like a glass bottle. Slightly heat the carrier oil (but only slightly!) and pour it into the bottle with the prepared ingredients. Close the bottle and wait for 2 weeks.
The same process but with alcohol is used when the ingredient doesn't have a lot of oil (like vanilla or cedar wood).
Once the extraction is done, you can use the oil to scent your home by many different ways like:
- putting a few drops into a scent lamp or fragrance block
- sticking one or several wooden sticks into the oil to help it evaporate
- mixing a small amount of isopropyl alcohol into it and letting it evaporate directly from the bottle